Vertical lift aircraft control



H. E. NEVILLE VERTICAL LIFT AIRCRAFT CONTROL Feb. 6, 1951 4 Sheets-Sheet 1 Filed Feb. 3, 1945 E L V...

mm ME Feb. 6, 1951 v H, E, NEVILLE 2,540,543

' VERTICALLIFT AIRCRAFT CONTROL Filed Feb. 5, 1945 4 Sheets-Sheet 2 a 8 34 l) l INVENTOR.

37I HARVEY E. Niv/LE ATTOHNEY Feb. 6, 1951 H. E. NEvxLLE 2,540,543

VERTICAL LIFT AIRCRAFT CONTROL Filed Feb. 5, 1945 4 Sheets-Sheet 5 llllllllWm/q/ lffm'llllll INVENTOR. HARVEY NEI/ILLE ATTRNEY Feb. 6, 1951 H. E. NEvxLLE 2,540,543

VERTICAL LIFT AIRCRAFT CONTROL Filed Feb. 3, 1945 4 Sheets-SheerI 4 IN V EN TOR.

Patented Feb. 6, 1951 UNITED STATES PATENT OFFICE 2,540,543 VERTICAL LIFT AIR-CRAFT rCONTROL Harvey E. Neville, Shaker Heights, `Ohio Application February 3, 1945, Serial No. 575,951

(Cl. rib-135.24)

20 Claims.

My invention pertains to vertical lift aircraft, and more particularly to means for controlling such aircraft.

An object of my invention is to provide simple yet rugged control means for vertical lift aircraft.

Another object of my invention is to provide a control system for vertical lift aircraft which terminates in a control box within the pilots compartment, and to have the control box' movable within said compartment.

Still another object of my invention is to provide a control system for vertical lift aircraft utilizing co-axial counter-rotating rotors as well as those utilizing a single rotor with a smaller torque compensating tail rotor.

It is also an object of my invention to provide a control system for vertical lift aircraft which is adaptable to mass production.

A further object of my invention is to provide a control system for vertical lift aircraft which can be easily replaced should trouble occur;

Other objects and a fuller understanding of my invention may be had by referring to the following description, claims and drawings wherein:

Figure 1 is a schematic diagram, partially in cross-section, of the details of a control system for vertical lift aircraft utilizing two counter-rotating rotors. Y

Figure 2 is an exploded schematic diagram, in isometric, of the same control system, andy Figure 3 is a schematic diagram, partially in cross-section, of the details of a control system for veitical lift aircraft utilizing a single rotor for lift and a torque stabilizing tail rotor.

Figure 4 is a cross-sectional view on an enlarged scale of a portion of the device shown inFig. 1.

There has long been a need for a simple, inexpensive yet rugged, and dependable control system for controlling the vertical, horizontal, and rotational (turning) motion of vertical lift aircraft.

My device provides such a control, and for a vertical lift aircraft having two co-axially mounted counter-rotating rotors such as are indicated by the reference Acharactersl II) and II in Figure 1, it comprises three manually operated control devices, I2, I3, I'4. These three control devices may be mounted in a box (schematically indicated by the dotted line I5) positioned within the pilots compartment, and the three individual controls may extend from inside the box I5 through the wall of the box to the outside thereof, terminating in knobs or handles whereby the Ipilot may readily operate them.

The control device I3 hasa stick or wheel 20 which may be tilted and which may also be turned. The tilting motion controls the horizontal motion of the aircraft and the turning motion the rotation of the aircraft about its vertical axis. The control device I2 has a handle 2| which may be turned to change the relative positions of the two rotors II) and II, for reasons more fully described later. The control device I4 includes a handle 22 for controlling the vertical Amotion of the aircraft.

The control wheel 2B is mounted by means of a universal joint 25 on a base 26 which has an enclosed central open portion 21. Within the open portion is a plate 28 floating on pins 25 which are anchored in the top and bottom walls of the base 25. A yoke 30 has a threaded shaft 33 extending through the floating plate 28. The yoke 30 is connected to shaft 20 of the wheel 20 by means of the spider 3|, and the joint 32 allows pivotal motion of the wheel and shaft 2i), 2ll"with respect to the yoke 30. When the wheel 20 is turned, thereby turning the threaded shaft 33 with respect to the plate 28, the floating plate 28 is moved up or down within the open space 2l depending upon the direction of turning, and the hydraulic bellows device 34 which is mounted between the plate 28 and the base 26 is caused to expand or contract. A plate 35 having a raised central portion 35 is connected to the wheel shaft 20' in such a way thatit does not rotate with the shaft and yet is rigidly held axially with respect to the shaft. The bottom face 3S of the plate 35 defining a plane and three or more hydraulic bellows devices, 3'I, 3B, and 39 (only two are shown in Figure l; see Figure 2) are positioned between the top face of the base 26 which defines a plane and the bottom face 36 of the plate 35, which, when in its neutral position, defines a plane parallel to the plane of the base 26. Tilting motion of the control wheel 2i) in any direction will tip the plate 35 in the same direction and to the same extent, and this will depress some of the bellows and extend others in accordance with the degree and direction of movement.

The hydraulic bellows 31, 38, and 39 are connected respectively, to the ends of the hydraulic lines 3T', 38', and 39', and hydraulic bellows 4l, 48, and 49 are connected, respectively, to the other ends of the hydraulic lines. The bellows 41, 48, 49 are mounted between a iiat plate 46 having an integral ball A46' which comprises part cfa universal joint and a wobble plate 45 whose underneath surface defines a plane which normally is parallel to the plane defined by plate 46. The

'to the shaft 9. 'bellows engages a portion of one of the rotor wobble plate l5 is mounted on the ball 46 for tilting motion with respect thereto. Tilting of the plate 35 by the control wheel 20 causes, by hydraulic transmission, a corresponding tilting of the wobble plate 55. The plane dened by the upper surface of the wobble plate 45 passes through the center of the universal joint which is indicated in its entirety by the reference character 50.

Two pairs of followers 53, `5|and 55, 56 engage the upper surfaces of the wobble plate 45 and each pair controls the pitch motions of one the rotors Iii, il. The two pairs of followers 53, 54 and 55, 55 are shown in Figure 2. In Figure l I show, for the salie of clarity, only one pair, namely 55, 55, which control the pitch oi-rotor The pair of followers 55, 55 (Shown as hydraulic bellows), engage the upper surface of the wobble plate 5 and are in hydraulic-communication with hydraulic lines A55 and 55 which extend through the arms V5i and 58 (two similar arms hold the bellows 55, 55 but are not shown inlFigure l) for transmitting hydraulic Ypressure as-the bellows 55, 56 are squeezed or extended between the wobble plate d5 and the ends of the arms 5'?, The arms and 58 are extensions 'ofthe-shaft 9 on which the rotor lil is mounted -androtate-with respect to non-rotatable wobble -plate l:7,5 as the rotor i5 is driven by the motor 8 Lto the manner in which the bellows 55, 56 ride aroundthe wobble plate 5.

'I'he rotor i@ is connected to the shaft 9 and the rotor i is connected to the shaft l in a manner to permit independent pivotal motion of cachot the two blades of the two rotors about their longitudinalaxcs with respect to the axis ofthe shafts. The amount of pivot or pitch of these rotors controls the night of the aircrafta's -is -well known to one skilled in the art.

'For controlling the rotor I mount a pair of hydraulic `bellows units 5U, 6|, one for each rotor blade, on extension plates 62, 63' connected rEhe upper end of each ofthe blades at a point offset from its longitudinal axis 4so that extension of the bellows will change the pitch of the blade, and compressed springs 64,

55 are mounted between the blades and fixed extension plates 65, Gl for changing the pitchiof the blades when the bellows contract. The blades of rotor El are similarly mounted between bellows l0, 'li and springs i2, 13. The bellows are mounted on extension plates M, 15 and the 'springs on extension plates 76, 71.

As I have mentioned, Figure l shows only two arms 51, 58

`carrying on their ends bellows 55, 56 for controlling the rotor similar manner to control the bellows 60, 6| associated with the rotor l5. Changing the pitch of the rotors cyclically during their rotarymotion .controls the horizontal motion of .the aircraft.

Uniformly changing the pitch of oneof the rotors in one direction by a certain fixed amount and simultaneously changing the pitch of the other rotor by the same amount but in the opposite direction causes the aircraft to slip about its vertical axis. This control action is obtained by turning control wheel 20 thereby raising or lowering the plate 28, and compressing or extending the bellows unit 313. Connected to the bellows unit 34 is a hydraulic line 35 leading to two or more hydraulic .bellows 184,85, 86 positioned between a stationary plate 8l and one end of each `of the levers 83, 88, 89, respectively. The levers "88, 89 (shown in Figure l) are pivoted at 5|), 9|.

.Between the bellows units and the pivot points each of the levers is connected to an annular ring '92, and onthe-other side of the pivot points the leversnareconnected to a central disc 93. The points of connection between the levers and the ring-andthe levers and the disc are equally spaced on either side of the pivot points of the .three levers. Accordingly, when the levers are actuatedby the hydraulic bellows the plate 93 and the disc 92 will move equal amounts in oppo- ,sitedirections and will maintain their parallel relationship.

`.Two pairs vof hydraulic bellows units 9B, 95 .and 9E, 91 are connected, respectively, to the extended arms 5l an-d ,58 and to two similar arms (not. shown) .and rotate as the arms rotate. The disc 92 and thel plate 53 do not rotate, and sothe bellows 594,95, 55, 9| may be termed followers .The bellows eil communicates hydraulically with the hydraulic line 55 leading to the bellows unit 10 which controls one blade of the rotor and the bellows 95 communicates hydraulically with :the hydraulic line 56 leading to the bellows unit `i'l which controls the other blade of the rotor The bellows 95, ,Si communicate with bellows.60,6| by means of hydraulic lines 5ft', 53 '.andthcreby control the pitch of the blades of the rotor Thus the pitch of the two blades -of the :rotor il are equally controlled and in thesame sense. The bellows 96, 91 (shown in Figure 2) follow the disc 93 and transmit control V`pressures through the hydraulic lines 54', 53 to the bellows 55, 5l which control the pitch of -theitwo blades 'of the rotor l5. As the ring 92 and the disc 93 move equally but in opposite .direct-ionsfthe rotors l| and I@ have their pitch controlled equally but in an opposite sense, thus controlling the turning motions of the aircraft.

The controllever 22 is mounted by means of a` pivot |00 in a housing 15| and when it is moved it compresses or extends a bello-ws |02. The movement ofthe lever 22 simultaneously changes thepitchinlboth of the rotor blades lil and to control the up and down movement of the aircraft. vThis is done in .the following manner. Bellows H|02 is connected by means of the hydraulic line |52 to the bellows |53 which is supported between a fixed plate 504i and the plate Al :which supportstheuniversal joint 50. The hydraulic forces are thereby transmitted from the bellows |02 to the'bellows |03 thereby raising :or lowering the plate v|36 with respect to the xed plate |54. When the plate 156 is moved :with respect tothe'ixed plate Ili the `parallel relationship is maintained. Thus the bellows 53, 54 and 55, 56 are compressed or extended by Yequal amounts nomatter whether the plate 45 is tilted `or is parallelto the plate 5. YCompression or :extension of the bellows 53, 54 and 55, 56 willactuate the bellows `associated with the respective blades of rotors l5, to-change the .'pitchof the bladesby equal amounts, as has been previously described. The arrangement of the hydraulic followers 53, 54 and 55, 56 is such that the angle or pitch of the rotor blades will be the same at two xed diametrically opposite points on their circle of rotation (no matter in which direction the blades are rotated) when only the wobble plate 45 is controlling the blades. This will permit horizontal motion of the aircraft in either direction perpendicular to the diameter connecting these two fixed points, when the control stick 20 is tipped in either direction. In my invention I add a device indicated generally by the reference character I||l to change the relative phase position of one set of rotor blades with respect to the other set of rotor blades within a limit of 180 degrees. This is done without interrupting the rotation of either rotor and will alter the azimuthal relation between the points on the circles of rotation of the respective rotors at which the pitch of the rotor 'blades is maximum. This permits varying the direction of the horizontal component of thrust acting on the aircraft. This will cause horizontal motion of the aircraft in any direction.

The counterrotating shafts 'I and 9 are normally geared to the drive shaft of the motor 8 in sucha manner that their rotation is positive with relation toeach other. This positive relationship can be altered by a small amount (not over 180 degrees), and hydraulic couplings 80, 8| permit the transmission of hydraulic pressures from the bellows 55, 94 to the bellows 10, and from the bellows 56, 95 to the bellows 1| no matter what the rotational position of the shaft 9 is with respect to the shaft 1. l

The rotor blades are driven by the motor 8 through a clutch device and through two gears |I2 and |I3. The gear ||2 meshes with the gear I I4 and the torque is transmitted to the gear I I5 which is in toothed engagement with the gear IIB. The gear ||6 drives the shaft 9 on which is mounted the rotor I 0. .The gear I I3 through gears I|1 and IIB and ||9 drives the shaft 1 on which is mounted the rotor The device Ill) for changing the relative phase position of the rotor I with respect to the rotor II comprises the two pinion gears I4 and I I5 which are connected together by a helical spline |20. The two pinion gears I |4 and I5 are held against axial movement by the framework |2| `but the shaft |22 is free to move under the influence of forces from the bellows |23 transmitted through bearing |23. The gear II4 is mounted on a splined section of the shaft |25 in such a way that rotational drive is positive. However, if the shaft |20 is moved axially by the bellows |23` in order to compress the spring |24 no relative ro` tational motion of the gear ||4 with respect to the shaft |20 takes place. however, is mounted on thehelically cut spline portion of the shaft |20 in such a way that the gear is rotated relative to shaft |20 within the limit of 180 degrees by the axial movement of the shaft |20. The bellows |23 which is utilized for moving the shaft |20 back and forth is connected by means of the hydraulic line |25' to the bellows |25 in the control compartment. The bellows |25 may be compressed or extended by turning the handle 2| which by means of a threaded shaft |26 causes the floating plate |21 to move up and down in the hollow portion |28 of the housing |29. The plate |21 is pinned within the housing by means of pins |30. When the plane is in flight and the pilot wishes'to control the horizontal motion of the aircraft he does The other gear II5,

so by turning the handle 2|. As has been explained this, through the helical spline |20, causes a phase displacement of the rotor I0 relative rto the rotor II but only for a very limited angular displacement, that is, within 180 degrees. It does not change the location of the hydraulic followers which are in contact with the wobble plate and accordingly allows the blades of both rotors to intercept their respective hydraulic followers at any point on the circle of rotation at the will of the pilot. f

The fluid columns from the lower bellows to the upper bellows might oscillate if they are too long, so it is within the scope of my invention to mount the wobble plate up near the rotors I9, II, thereby reducing the length of the fluid columns. However, I prefer to have the wobble plate and its followers within the fuselage of the plane where they are protected from ice. Proper design o-f the hydraulic lines, including factors such as the length of the lines, their diameter, the uid used, and the rate of rotation of the rotors can be such as to reduce oscillation; and furthermore, special damping devices may be used.

In Figure 3 there is illustrated a modified form of my control system wherein the aircraft has only a single overhead rotor and utilizes a tail rotor |35 to counterbalance the torque of the overhead rotor.

The control device |3 may be constructed exactly like the control device I3 in Figure l, and may control the single rotor IB in the same manner as the rotor` I5 of Figure 1 is controlled. Figure 3, however, illustrates a modification wherein the hydraulic follower systems 55 and 56 of Figure 1 is replaced by a mechanical follower system. The mechanical follower system is comprised of two mechanical links or power transmitting devices 55-A and 56-A, one for each of the blades of the rotor I0, whose lower ends are in engagement with the top surface of the wobble plate 45, and whose upper ends are connected to the rotor blades in such a manner that as the blades and followers rotate around the stationary wobble plate 45 the followers cause the pitch of the blades to change in accordance with the tilt of the wobble plate.

The bellows 34 whichis compressed or extended by turning the wheel 2D is connected by means of hydraulic line 34' to the bellows |35 mounted in the tail of the aircraft. One end of the bellows |35 abuts against the xed plate |36 and the other end abuts against the movable plate |31 in such a manner that as the bellows expands it compresses the spring |43 and as it contracts it allows the spring Ido to expand. Connected to, the movable plate |31 are two arms |38 and |39. The arm |38 engages a projection |4| on the rotor blade |42 and the arm |35 engages a similar projectionl on the rotor blade |43, and as the plate |31 moves in accordance with the pressures applied to the bellows |35 its transmits the motion to the rotor blades |42, |43. The projec tions on the rotor blades are at a distance from the longitudinal axis of the rotor blades and the blades are pivotally mounted. Accordingly, the pitch of the blades |42, "|43 is changed in response to the turning of the wheel 29. Power for rotating the tail rotor |39 may come from the motor by any suitable power transmission train.

While I have shown bellows devices it is to be understood that hydraulic piston devices may also be used. It is also possible to use mechanical followers in the place of the hydraulic followers 7 53, 54 and 55, 55, although the hydraulic (bellows or pistons) are preferred. It is also within the scope of my invention to utilize a mechanical linkage system for actuating the helical spline l20 in Figure l.

The hydraulic lines |25', 3?', 313', 38, 39 and |02/ may be exible, and when such is the case the boX I5 within which the control units I2, I3, and t4 are mounted may be moved about in the pilots compartment.

While I have described my invention with a certain degree of particularity it is to be understoodthat numerous changes can be made in the parts and their relation to each other without departing from the spirit and scope of my invention.

I claim as my invention:

1. In a vertical lift aircraft having two multibladed rotors which rotaterin opposite directions' about a substantially vertical axis andthe blades of which are mounted for pivotal or pitch motion about their horizontal axes; rst control' means actuated by the pilot of said aircraft for controlling` the horizontal motion of said aircraft, said first control means including a tiltable plate defining a plane whose position is tilted by actuation of said rst control means only, a single wobble plate defining a plane, at least three control circuitsconnected to said tiltable and wobble plates and operated by the tilting motions of said tiltable plate for causing said wobble plate to tilt accordingly, first and second rotor bladeY control circuits controlled by the tilting motions of said wobble plate and extending from said' wobble plate to the blades of said rstand second rotors respectively to simultaneously cause cyclic changes in the pitch of said rotor bladesf during eachirotation thereof; pilot actuated second control means including a vertical lift control circuit connected to sa'id-v wobble plate for moving said wobble plate from one position denngna plane toa second position dening a planeV parallelto said first plane, said motion from one plane to another plane parallel thereto controlling both of Said rotor bladepitch control circuits simultane-V ously,v tocause a like non-cycliochange in the pitch of the blades of both rotors.

2. In a vertical lift aircraft having twormultibladed rotors the blades of each of `which `are mounted for pivotal or pitch motion about their longitudinal axes; first control means actuated by the pilot of said'aircraft, and including a tilt'- able plate defining a plane whose position is tilted` by actuation of said nrst control means, a wobblel plate defining a plane, at least -threeicontrol circuits connected to said tiltableA and wobble'- plates and operated by the tilting motions of saidtiltL able plate for causing said wobble plate'to tilt accordingly, rst and second rotor blade control circuits controlled by the tilting motions of-saidwobble plate and extending from said' wobble plate to the blades of said first and second rotors respectively to simultaneously cause cyclic changes in the pitch of said rotor blades during rotation thereof; pilot actuated secondcontrl means including a control circuit connectedto said wobble plate for moving saidwobble plate fromfone position defining a plane to a secondposition'dening a plane parallel to saidfirst plane, said motion from one planey tof another plan'e parallel theretov controlling both of said rotor blade pitch control circuits simultaneously to causealikenon-cyclic changein the pitch of both of said rotors.v

3." In' a vertical lift aircraft asset forthf'ir claim'- amd-543 8 l, the further characterization that said control circuits are hydraulic circuits.

4. In a vertical lift aircraft as set forth in claim l, the further characterization that said at least three control circuits are hydraulic circuits including at least three bellows means one in each circuit actuated by said tiltable plate and including at least'three bellows means one in each circuit in force transmitting relationship with said wobble plate, each of said at least three control circuits extending from one of the bellows 'means actuated by said tiltable plate to one of the bellows means in force transmitting relationship with said wobble plate.

5. Inl a vertical lift aircraft as set forth in claim l, the'A further characterization that said at leastY three control circuits are hydraulic circuits, and the vertical lift control circuit is also a hydraulic circuit.

6; In a vertical lift aircraft as set forth in claim 2, the further characterization that said control circuits are hydraulic circuits.

7. In a'y vertical lift aircraft as set forth in claim 2, the further characterization that said at least three control circuits are hydraulic circuits including at least three bellows means one in each circuit* actuated by said tiltable plate and including' at least' three bellows means one in each circuit in forcel transmitting relationship with said wobble plate, each of said at least three control circuits extending from one of the bellows means-actuated by said' tiltable plate to one of the bellows means in force transmitting relationship withsaid-vwobble plate.

8. In a control system for'vertical lift aircraft having two coaxially mounted counter-rotating rotors, an engine; rst power transmission means from saideiigin to the first of said rotors, second power transmission means from said engine to the second of said'rotors, the second of said power transmissionV meansV including phase shifting means for rotating one of said rotors with respect to the other of said rotors by an amount not greater' thanl 180 degrees, land control means connected-'to'said` phase shiftingmeans and actuatable bythe' pilot of said aircraft'fol` con-V trolling'said phase shiftingV means. g

9. Inacontrolsy-ste'm asset forth in claim 3, the further characterization that said control means is `a hydraulic system.

l0. In a control system' as set forth in claim 8, the further characterization that said rst and saidsec'ond' power transmission means each directly couplesone of the said rotors to said engine `and include gear means, and said second transmission meansincludes a helical spline gear driven by-said engine and means for mounting said spline gear for axial motion with respect to a piniongear which meshes with said helical spline gear'a'n'd alsom'esheswith means for rotating 'oneof Ysaid rotors, and means whereby said con-trol means',A upon being actuated, moves said helical spline gear axiall-y to cause said pinion gear to rotate.

ll. In 'a cont-rol system laso set forthin claim 8, the'further characterization that saidrst and said'secon'd powertransmission means comprise gear'chain'sf each ofw'hich directly couples one of the'- rotrs-to-the 'said engine, the said gear chain ir`r the said transmission means which includes 'means forindependently rotating a rotor including 'a helical spline gearfdri'ven byA said en gine and'mes'hin'gwitha pinion gear for rotating saidrotor, means for mounting said helical spline gear without interrupting the transmission of power from said engine to s aid rotor, and means whereby said' control means, upon being actuated, moves said helical spline gear axially to cause said pinion gear to rotate.

.12. In a vertical lift aircraft, a first and a second multi-bladed rotor, a first drive shaft connected to said first rotor and a hollow second drive shaft connected to said second rotor coaxially mounted around said rst drive shaft, a first power transmission means connected to said first drive shaft and a second power transmission means connected to said second drive shaft; said first and said second power transmission means including means for driving said two drive shafts in opposite directions whereby said two rotors move in opposite directions, means for controlling the pitch of the blades of said rotors and including only a single wobble plate and follower means in engagement with said single wobble plate for controlling `the pitch. of the blades of both of said rotors during rotation of said rotors, said wobble plate being mounted below the end of said second drive shaft whereby it and said follower means may be positioned within the aircraft for protection from the weather, and one of said power transmission means including means for rotating one of said rotors with respect to the other of said rotors thereby shifting the phase relationship of said first and second rotors.

13. In a control for a vertical lift aircraft having a rotor with a plurality of blades; a wobble plate; rst pilot actuated control means connected to said wobble plate for determining the tilt position of said wobble plate; a plurality of blade actuating means, one for each of said blades; a plurality of hydraulic circuit means, one for each of said blades, in engagement with said wobble plate and each in engagement with one of said blade actuating means for cyclically controlling the pitch of the blades in accordance with the tilt position of said wobble plate; second pilot actuated control means; a plurality of hydraulic compression and expansion units, one for each of said blades, controlled by said second pilot actuated control means; means connecting each of said hydraulic compression and expansion units respectively to a different one of said hydraulic circuits whereby each of said blade actuating means is served by only a single hydraulic circuit and each of said blades is simultaneously controlled through said circuit in accordance with the algebraic summation of the fluid displacement produced by the two control motions of the pilot.

14. The invention as set forth in claim 13, further characterized in this: that said first and second pilot actuated control means include a single common control which the pilot moves in two distinct manners vto effect two control operations on said blades.

15. In a control for a vertical lift aircraft having a rotor with a plurality of blades; a wobble plate; rst pilot actuated control means connected to said wobble plate for determining the tilt position of said wobble plate; a plurality of blade actuating means, one for each of said blades; a plurality of hydraulic circuit means, one for each of said blades in engagement with said wobble plate and each in engagement with one of said blade actuating means for cyclically controlling the pitch of the blade in accordance with the tilt position of said wobble plate; a second pilot actuated control means; a plurality of hydraulic compression and .expansion units, .one for each of said blades, controlled by said second pilot actuated control means; means connecting each of said hydraulic compression and expansion units respectively to a different one of said hydraulic circuits whereby each of said blade actuating means is served by only a single hydraulic circuit; and a third pilot actuated control means including means for moving said wobble plate.

from one position t0 another parallel position,

` whereby each of said blades is simultaneously controlled through its hydraulic circuit in accordance with the algebraic summation of the uid displacement produced by three control motions of the pilot.

16. In a control system for a vertical lift aircraft having a first and a second multibladed rotor, pilot actuated control means, hydraulic means controlled by said control means, a pivoted member in engagement with said hydraulic means and adapted to move in accordance with pilot induced displacements within said hydraulic means, a first and a second movable member connected to said pivoted member on opposite sides of said pivot point, rst connection means including hydraulic line means in engagement with said rst movable member, first actuating means connected to said rst connection means for controlling the pitch of the blades of said rst rotor, and second connection means including hydraulic line means in engagement with said second movable member, second actuating means connected to said second connection means for controlling the pitch of the blades of said second rotor; said control means controlling the degree and direction of pivoting of the aircraft about its rotor axis.

17. In a control system for vertical lift aircraft having two coaxially mounted counterrotating rotors, an engine, a rst power trans.. mission means from said engine to the rst of said rotors, a second power transmission means from said engine to the second of said rotors, the second of said power transmission means including phase shifting means for rotating one of said rotors with respect to the other 0f said rotors and control means connected to said phase shifting means and actuatable by the pilot of said aircraft for actuating said phase shifting means.

18. In a vertical lift aircraft the combination comprising two multibladed, counterrotating rotors; means for individually cyclically controlling the blade pitch of both of said rotors in accordance with pilot control motions, including a single wobble mechanism, pilot controlled means connected to the wobble mechanism for positioning the wobble mechanism, and means interconnecting the wobbley mechanism with the blades of said two rotors; said single wobble mechanism being the sole wobble mechanism between the pilot controlled means. and the blades of said rotors.

19. A vertical lift aircraft as set forth in claim 18, further characterized by second pilot controlled means connected to said wobble mechanism for positioning the wobble mechanism for simultaneous, uniform pitch change of the blades of both of said rotors.

20. A vertical lift aircraft as set forth in claim 18, further characterized by other pilot controlled means connected to the blades of both of said rotors by said means interconnecting the wobble mechanism with the blades of said two rotors for simultaneous mean differential pitch change of HARVEY E. NEVILIE;

REFERENCES CITED The` following references are of record ni the le of this patent:

UNITED STATES PATENTS Number Name Date Dorsey Apr..51927 Smith ,Dec; 15, 1931 Evrard June. 21, 1932 Breguet July 18 1933 Number Number- Name Date Bordoni Aug. 8, 1933 Upson Nov. 19, 1935 Myers Feb. 16, 1937 Young Sept. 23, 1941 Cox Feb. 12, 1946 Trice ,Apr. 23, 1946 Thomson Nov. 5, 1946 Hoover Jan. 27, 1948 Hardy Dec. 13, 1949 FOREIGN PATENTS Country Date Great Britain Jan. 29, 1923 

